Maximum pressure selector



Nov. 19, 1968 I R. E. BOWLES MAXIMUM PRESSURE SELECTOR Filed July 31, 1964 12 B FIG-Z $16.1 I *9 2F: 6. 6 gizzzrtrifi 46 48 INVENTOR RoMALo E. BOLULES BY ZM% .0

ATTORNEY$ United States Patent 3,411,520 MAXIMUM PRESSURE SELECTOR Romald E. Bowles, 12712 Meadowood Drive, Silver Spring, Md. 20904 Filed July 31, 1964, Ser. No. 386,492 23 Claims. (Cl. 13781.5)

The present invention relates to pressure selector apparatus and, more particularly, to a pure fluid pressure selector apparatus for producing an output signal having a pressure substantially equal to the highest pressure of a plurality of distinct input pressures applied to the apparatus.

It is an object of the present invention to provide a pure fluid apparatus having a plurality of input channels directed towards a single output channel wherein the pressure in the output channel is substantially equal to the highest pressure of the pressures of the various input signals.

It is another object of the present invention to provide a pure fluid maximum pressure selector which may be employed as a pure fluid amplifier to produce a pulsating output signal that equates to the highest positive pressure in two channels having differentially related, pulsating signals therein.

It is another object of the present invention to provide a pure fluid maximum pressure detector which is capable of producing an output signal having a pressure substantially equal to the highest pressure of a plurality of pressure signals, such a system providing for comparison and control of variable pressure systems.

The above and still further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed description of one specific embodiment thereof, especially when taken in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a diagram illustrating One form of appaatus of the present invention;

FIGURE 2 is a diagram illustrating fluid stream characteristics which must be considered in developing a maximum pressure selector in accordance with the present invention;

FIGURE 3 is a diagram illustrating some of the principles of the apparatus of FIGURE 1 FIGURES 4a and 4b are flow diagrams illustrating changes in flow patterns of intersecting streams;

FIGURE 5 is a diagram illustrating a four-way rectifier circuit employing the maximum pressure recovery unit of the present invention; and

FIGURE 6 is a diagram illustrating a maximum pressure recovery unit having three input signals.

Referring now specifically to FIGURE 1 of the accompanying drawings, there is illustrated a maximum pressure selector generally designated by the reference numeral 1 and having a pair of input passages 2 and 3 formed as channels in a solid block of material 4. The passages 2 and 3 are supplied through appropriate apertures 6 and 7 which pass through the bottom of the block 4 as illustrated in FIGURE 1. The centerlines of the passages 2 and 3 converge and meet at a point 8 which, in the particular configuration illustrated, is at the entrance to asingle output passage 9 also formed as a channel on the block 4. The space intermediate the outlet orifice of passages 2 and 3 and inlet orifice of the passage 8 is recessed to the depth of the passages and is confined between a wall 11 of the body 4 and top or cover plate 12. The plate 12 is illustrated in broken lines.

Certain parameters of the apparatus illustrated in FIG- URE 1 are critical and initially reference is made to FIGURE 2 of the accompanying drawings. In this figure, a nozzle 13 issues a stream of fluid to the right. While the fluid is in the nozzle or passage 13, substantially all of the fluid is at the same dynamic pressure. Upon leaving the nozzle, the fluid begins to entrain fluid surrounding the stream and, since this fluid is at a lower velocity, averaging causes the dynamic pressure to fall. At the right of the nozzle 13, there is illustrated a triangle 14 having a base equal to the width of the nozzle and having two equal-length legs. The triangle 14 illustrates the region of the stream in which the dynamic pressures of the stream is equal to the initial dynamic pressure; that is, the pressure of the fluid in the nozzle 13. In ordinary situations such as an air stream traveling through a region of ambient air, the region of initial pressure converges as indicated by the triangle 14 and the apex of th triangle lies about six widths of the nozzle 13 downstream from the egress orifice thereof.

The above factor must be taken into account in the apparatus of FIGURE 1. In order to insure that a maximum of the fluid entering the passage 9 still moves at the initial speed and therefore the initial total pressure of the stream, the channel 9 should be as close to the passages 2 and 3 as possible so as to maximize the amount of fluid having maximum pressure entering channel 9. However, the factor of maximum pressure is not the only controlling factor in the system. If the point of interaction between the streams issued by the passages 2 and 3 is too close to the passages, then the static pressure buildup due to interaction of the streams feeds back into the passages and alters the input signal impedance so as to adversely affect the input signal pressure and flow conditions. It has been found that the point of interaction of these two streams should be downstream of the egress orifice by at least two widths of the egress orifice of the input passages for best operation. As long as the point of intersection is at least two orifice widths downstream, the static pressure build-up may be dissipated through the space between the bottom wall 11 and the top plate 12 and the pressure-flow conditions in the passages 2 and 3 remain adequately decoupled. If the outlet passage 9 is sufliciently small to monitor only a very narrow region along the centerline of the device, then it is possible to go as far downstream as six widths of the nozzles 2 and 3 and produce an output pressure closely related to the maximum pressure in one or the other of the passages 2 or 3. As a practical matter however, it is found that a desirable range for operation is to locate the egress orifice of the channel 9 at a distance downstream from the egress orifices of the passages 2 and 3 equal to two to four times the egress orifice width. So long as this constraint is observed, it is found that very excellent results can be obtained; that is, the output pressure substantially follows the maximum pressure applied to the system. The other constraint on the system is that the inlet to the passage 9 be small compared to the egress orifice of the supply passages. More particularly, the width of the ingress orifice of the passage 9 should be no greater than one-half of the width of the egress orifices of the passages 2 and 3. One other restraint on the system is the angular relationship between the two or more inlet passages. This is expressed as follows: The ingress orifice of the passage 9 is preferably located at the point of intersection of the centerlines of the passages 2 and 3 or one ingress orifice width upstream or downstream of this point. The effect of this variable is illustrated in FIGURE 3 of the accompanying drawings.

Referring now specifically to FIGURE 3, nozzles 16 and 17 issue two streams of fluid whose centerlines intersect at apoint 18. The adjacent or inner peripheries or sides of the streams issues by nozzles 16 and 17 intersect at a point 19. A line 21 represents the ingress orifice to the receiver passage located at the intersecting point 18 with the ingress passage having a width equal to one-half of the width of the egress orifices of the passages 16 and 17. The ingress orifice 21 of the receiver passage is located four nozzle widths downstream of the egress orifices. A line 21a indicates the location of the ingress orifice of the outlet passage when located one orifice width upstream of the point 18 of intersection of the centerlines of the streams. A line 2121 represents the position of the ingress orifice of the outlet passage when it is located one orifice width downstream of the point of intersection 18 of the centerlines of the streams.

Assuming that the righthand stream, as viewed in FIG- URE 3, is the stronger stream and drawing lines from the point of intersection 19 to the lefthand end of each of the lines 21, 21a and 21b, it is possible to estimate the relative pressures of the streams at which some of the lower pressure stream begins to enter the outlet passage. A fourth line is drawn up the center of the device from the point 19. The lines in the order in which they have been described are lettered a, b and c and the centerline is d. When the two streams are equal, the streams converge and proceed parallel to the line d; that is, the vector diagram produces a final vector having an equal angle relative to the original two vectors. In this case, of course, the pressure in the output orifice should be equal to both maximum pressures.

The diagram of FIGURE 3 seems to indicate that the orifice, for instance 21, straddles regions part of which are of the maximum pressure and part of which are at the reduced pressures due to entrainment. However, when the two streams converge, the regions of maximum pressure do not remain symmetrical with respect to the streams but move towards each other; that is, move towards the barrier which each stream presents to the other stream. This phenomenon is explained with respect to FIGURES 4a and 4b. In FIGURE 4a, the stream patterns are drawn as if the streams do not intersect. The point of intersection of the centerlines is designated by the reference numeral 22, and the ingress orifice of an outlet passage is designated by the numeral 23. The adjacent regions of the streams which are below maximum pressure are designated by reference numeral and the maximum width of the combined lower velocity regions is designated by line 25. It will be noted that the line 25 is almost as long as the line 22 which seems to indicate that the majority of the fluid that would enter the outlet orifice would be fluid having a pressure below maximum pressure. This is based upon the reasoning that when the two streams intersect, being equal, all flow lines are turned to flow vertically upward as viewed in FIGURE 4a. However, this is not the case and the flow patterns alter materially when the streams intersect.

FIGURE 4b represents the actual conditions when two streams intersect. In FIGURE 41), it will be noted that, as the streams converge, the maximum pressure region of each stream in effect moves towards the center of the configuration. The lower velocity fluid which exists between these two maximum pressure regions is compressed and becomes a smaller portion of the total stream than these regions of fluid represented immediately prior to confluence of the two streams. Also, due to the entrainrnent effect resulting from momentum of the intersecting streams, the velocity and associated total pressure in the lower pressure region 20 are raised very close to the maximum velocity and associated total pressure of the streams. Due to these effects and the location and size of the orifice 22, over ninety-five percent of the fluid entering the orifice 22 is effectively at the maximum total pressure of the system and the remaining portion of the fluid is almost at the maximum pressure. Thus, the total pressure of the fluid entering the ingress orifice 22 of the output passage is substantially equal to the maximum total pressure of the system. Under the conditions described in FIGURE 4b, the pressure at the ingress orifice 22 to the outlet tube is a minimum of ninety-five percent of the maximum pressure of the fluid streams. Depending upon various design parameters which relate to the Reynolds number of the fluid, the pressure ranges over which the system operates etc., systems can be designed which provide an output pressure of 98-99 percent of the maximum input pressure to the system.

This percentage holds even though the lefthand stream may have a smaller pressure than the righthand stream and the precise condition illustrated in FIGURE 4b is not achieved. The reason for this is that the centerlines of the jets are caused to intersect at a region which is very close to the receiving aperture regardless whether it is in the position 21, 21a or 21b of FIGURE 3 and therefore there is insuflicient length for the low pressure jet to produce any appreciable deflection of the high pressure jet. Thus, the lower the pressure of the lefthand stream, the smaller the portion of this jet which tends to enter the outlet passage. In consequence, the system is inherently selective in that the proportion of the lower pressure stream entering the outlet tube decreases with decrease in its pressure. Also, as indicated, the maximum pressure regions of the streams tend to move toward one another when the streams intersect and in so doing compress and reaccelerate the lower total pressure fluid between the two higher pressure regions and raise the total pressure of the lower pressure region towards the higher total pressure level. This is readily seen in FIGURE 4b. In a system where the two streams are of equal total pressure, the maximum effect of the lower total pressure fluid entering the receiving aperture is to reduce by five percent the total pressure indicated and is usually considerably less.

As stated above, and reference is again had to FIGURE 3, the location of the ingress orifice to the outlet passage, relative to the point of intersection of the centerlines of the streams, has an effect upon the total pressure region captured. However, these relationships are not quite as clear as might be thought by observing FIGURE 3. It would appear that the best location of the ingress orifice is as indicated by reference numeral 211), since it takes a smaller deflection of the lefthand stream to exclude it from the egress orifice. On the other hand, the lefthand stream has a longer distance in which to act to deflect the main stream so that some of these effects cancel one another. As a result, the best location of the ingress orifice in a given system depends upon other factors such as the pressure ranges over which the streams are variable, the Reynolds numbers of the fluids and other conditions of the fluid rather than of the structure.

As previously indicated, the ingress orifice is smaller than the egress orifices of the passages 16 and 17 so that the output passage sees the maximum pressures of the streams rather than an average including the adjacent and non-adjacent minimum and maximum pressure regions. A size of the ingress orifice equal to the one-half size of the egress orifice of passages 16 and 17 has been found to give very good results.

In the apparatus of FIGURE 5, there is provided a full wave fluid rectifier. The rectifier includes an analog amplifier generally designated by the reference numeral 26 having a main power nozzle 27 and control or input nozzles 28 and 29 disposed on opposite sides of the device and oppositely directed relative to one another. The device also has two output passages 31 and 32. The right control passage 29 may be connected to a source of bias pressure P+ while the lefthand control nozzle 28 may be connected to a variable pressure source which varies the pressure of the system about the pressure P+ applied to the righthand nozzle 29. The variable pressure applied to the control nozzle 28 is, for purposes of explanation, taken to be a sinusoidal variable.

The outer passages 31 and 32 constitute the input passages to the maximum pressure selector to the present invention, the selector being designated by reference numeral 33 in FIGURE 5 and its output passage being designated by the reference numeral 34. The variations in pressure in the input passage 32 to the pressure selector 33 are illustrated above the passage 34 and constitute half sine waves designated by numerals 36 and 37. The pressure variation in the output passage 31 is designated by the reference numeral 38. The pressure in the output passage 34 follows the outline indicated by the darkened portion of the wave and thus the input signal applied to the control passage 28 is rectified to provide a pulsating unidirectional signal relative to the bias pressure.

The apparatus of the present invention is not restricted to two input channels and a three or more input channel device may be employed as illustrated in FIGURE 6 of the accompanying drawings. The operation of this device is essentially the same as the operation of the device of FIGURE 1. The essential feature of the system is that the ingress orifice 39 of an output passage 41 be sufficiently narrow relative to stream core widths and sufficiently close to the egress orifices 42, 43 and 44 of supply passages 46, 47 and 48, respectively, that the momentum of the various streams cannot average over both core and low velocity regions of the combined stream. This of course, must also be prevented in the apparatus of FIGURE 1 and this result is achieved by the placement of the ingress orifice 39 of the output passage 41 no more than six orifice widths downstream of the input passage orifices 42, 43 and 44 and by the small size of the output assage which looks only at the small center core of pressure of the system. So long as this type of arrangement is followed, the momentum will not add and a true maximum pressure selector can be achieved.

While I have described and illustrated one specific embodiment of my invention, it will be clear that variations of the details of construction which are specifically illustrated and described may be resorted to without departing from the true spirit and scope of the invention as defined in the appended claims.

What I claim is:

1. A pure fluid maximum pressure selector for providing a fluid output signal having a pressure which is always substantially equal to the highest pressure of a plurality of input pressure signals comprising:

at least first and second input passages having egress means for connecting said input passages to receive respective ones of said input pressure signals;

an output passage for conducting said fluid output signal located downstream of said input passages and having an ingress orifice;

said ingress orifice of said output passage being located downstream of said egress orifices of said input passages by a distance of between two and six times the width of said egress orifices;

the angular relationship between said input passages being such that their centerlines intersect in the region of said ingress orifice of said output passage; and

the region between said input and output passages having sufficient volume to maintain ambient pressure in said region.

2. A pure fluid maximum pressure selector for providing a fluid output signal having a pressure which is always substantially equal to the highest pressure of a plurality of input pressure signals comprising:

at least first and second input passages having egress means for connecting said input passages to receive respective ones of said input pressure signals;

an output passage for conducting said fluid output signal located downstream of said input passages and having an ingress orifice;

said ingress orifice of said output passage being located downstream of said egress orifices of said input passages by a distance of between two and six times the width of said egress orifices;

the angular relationship between said input passages being such that their centerlines intersect in the region of said ingress orifice of said output passage;

the region between said input and output passages having sufiicient volume to maintain ambient pressure in said region; the width of said ingress orifice of said output passage being at the most approximately one-half the width of each of said egress orifices of said input passages. 3. A pure fluid maximum pressure selector for providing a fluid output signal having a pressure which is always substantially equal to the highest pressure of a plurality of input pressure signals comprising:

at least first and second input passages having egress orifices; means for connecting said input passages to receive respective ones of said input pressure signals; an output passage for conducting said fluid output signal located downstream of said input passages and having an ingress orifice; said ingress orifice of said output passage being located downstream of said egress orifices of said input passages by a distance of between two and four times the width of said egress orifices; the angular relationship between said input passages being such that their centerlines intersect in the region of said ingress orifice of said output passage; and the region between said input and output passages having sufiicient volume to maintain ambient pressure in said region.

4. A pure fluid maximum pressure selector for providing a fiuid output signal having a pressure which is always substantially equal to the highest pressure of a plurality of input pressure signals comprising:

at least first and second input passages having egress means for connecting said input passages to receive respective ones of said input pressure signals;

an output passage for conducting said fluid output signal located downstream of said input passages and having an ingress orifice;

said ingress orifice of said output passage being located downstream of said egress orifices of said input passages by a distance of between two and four times the width of said egress orifices; the angular relationship between said input passages being such that their centerlines intersect in the region of said ingrees orifice of said output passage;

the region between said input and output passages having sufficient volume to maintain ambient pressure in said region;

the width of said ingress orifice of said output passage being at the most approximately one-half the width of each of said egress orifices of said input passages.

5. The combination according to claim 4 wherein said ingress orifice of said output passage is located at the intersection of the centerlines of said input passages.

6. The combination according to claim 4 wherein said ingress orifice of said output passage is located upstream of the intersection of the centerlines of said input passages by a distance equal to one width of said ingress orifice of said output passage.

7. The combination according to claim 4 wherein said ingress orifice of said output passage is located downstream of the intersection of the centerlines of said input passages by a distance equal to one width of said ingress orifice of said output passage.

8. The combination according to claim 4 further comprising:

at least a third input passage located between said first and second input passages;

said third input passage being coaxial with said output passage.

9. The combination according to claim 4 wherein said system comprises a rectifier device including means for introducing difierentially fluctuating signals into said first and second input passages.

10. A pure fluid rectifier comprising:

a fluid amplifier including a power nozzle, means for developing a fluctuating pressure gradient across a power stream issued by said power nozzle and a pair of output passages;

a pure fluid maximum pressure selector for providing a fluid output signal having a pressure which is always substantially equal to the highest pressure of a pair of input pressure signals including at least a pair of input passages having egress orifices, and an output passage for conducting said fluid output signal located downstream of said input passages and having an ingress orifice, said ingress orifice of said output passage being located downstream of said egress orifices of said input passages by a distance of between two and six times the width of said egress orifices, the angular relationship between said input passages being such that their centerlines intersect in the region of said ingrees orifice of said output passage, and the region between said input and output passages having sufficient volume to maintain ambient pressure in said region; and

means connecting said output passages of said fluid amplifier to said input passages of said maximum pressure selector.

11. The combination according to claim wherein:

the width of said ingresss orifice of said output passage is at the most approximately one-half the width of each of said egress orifices of said input passages.

12. The device of claim 1 wherein the centerlines of said input passages intersect downstream of said ingress orifice of said output passage.

13. The device of claim 1 wherein the distance between the ingress orifice of said output passage and the point of intersection of the input passage centerlines is no greater than the width of said egress orifices.

14. The device of claim 2 wherein the centerlines of said input passages intersect downstream of said ingress orifice of said output passage.

15. The device of claim 2 wherein the distance between the ingress orifice of said output passage and the point of intersection of the input passage centerlines is no greater than the width of said egress orifices.

16. The device of claim 3 wherein the centerlines of each of said input passages extend through said ingress orifice of said output passage.

17. The device of claim 3 wherein the distance between the ingress orifice of said output passage and the point of intersection of the input passage centerlines is no greater than the width of said egress orifices.

18. The device of claim 8 wherein the centerlines of each of said input passages extend through said ingress orifice of said output passage.

19. The device of claim 8 wherein the distance between the ingress orifice of said output passage and the point of intersection of the input passage centerlines is no greater than the width of said egress orifices.

20. The device of claim 11 wherein the centerlines of each of said input passages extend through said ingress orifice of said output passage.

21. The device of claim 11 wherein the distance between the ingress orifice of said output passage and the point of intersection of the input passage centerlines is no greater than the width of said egress orifices.

22. The device of claim 1 wherein the region between said input and output passages is bounded by at least one wall having at least first and second openings therein constituting said egress orifices.

23. The device of claim 4 wherein the region between said input and output passages is bounded by at least one Wall having at least first and second openings therein constituting said egress orifices.

References Cited UNITED STATES PATENTS 3,128,040 4/1964 Norwood 13781.5 3,266,509 8/1966 Bauer 13781.5 3,282,281 11/1966 Reader 137-815 3,122,165 2/1964 Horton 13781.5 3,191,612 6/1965 Phillips 1378l.5 3,212,515 10/1965 Zisfein et al. 1378l.5 3,238,961 3/1966 Hatch 137--81.5

OTHER REFERENCES H.D.L. Report, TR1114, Fluid Amplification, Logic Elements, 9, E. V. Hobbs, Mar. 8, 1963, pp. 16, 20 and 21.

Fluid Power International, Fluid Logic Devices and Circuits, A. E. Mitchell et al., July 1963, pp. 245, 246.

SAMUEL SCOTT, Primary Examiner. 

1. A PURE FLUID MAXIMUM PRESSURE SELECTOR FOR PROVIDING A FLUID OUTPUT SIGNAL HAVING A PRESSURE WHICH IS ALWAYS SUBSTANTIALLY EQUAL TO THE HIGHEST PRESSURE OF A PLURALITY OF INPUT PRESSURE SIGNALS COMPRISING: AT LEAST FIRST AND SECOND INPUT PASSAGES HAVING EGRESS ORIFICES; MEANS FOR CONNECTING SAID INPUT PASSAGES TO RECEIVE RESPECTIVE ONES OF SAID INPUT PRESSURE SIGNALS; AN OUTPUT PASSAGE FOR CONDUCTING SAID FLUID OUTPUT SIGNAL LOCATED DOWNSTREAM OF SAID INPUT PASSAGES AND HAVING AN INGRESS ORIFICE; SAID INGRESS ORIFICE OF SAID PASSAGE BEING LOCATED DOWNSTREAM OF SAID EGRESS ORIFICES OF SAID INPUT PASSAGES BY A DISTANCE OF BETWEEN TWO AND SIX TIMES THE WIDTH OF SAID EGRESS ORIFICES; THE ANGULAR RELATIONSHIP BETWEEN SAID INPUT PASSAGES BEING SUCH THAT THEIR CENTERLINES INTERSECT IN THE REGION OF SAID INGRESS ORIFICE OF SAID OUTPUT PASSAGE; AND THE REGION BETWEEN SAID INPUT AND OUTPUT PASSAGES HAVING SUFFICIENT VOLUME TO MAINTAIN AMBIENT PRESSURE IN SAID REGION. 